(1) Field of the Invention
The present invention relates generally to underwater connectors. More particularly, this invention relates to an improvement for underwater connectors having a flexible boot bonded onto a non-conductive electrical connector that reliably seals the interface between the boot and connector to assure long-term reliable operation.
(2) Description of the Prior Art
Referring to FIG. 1, prior art multi-pin electrical connectors 50 have connector housings 51 that are typically made from a conductive metal such as aluminum or stainless steel. Multi-pin electrical connector 50 can connect to an electrical cable 80 having a number of electrical conductors 52 (only one of which is shown in FIG. 1) in an end portion 55 having a collar-like threaded nut 56 or other securing device to engage a correspondingly shaped threaded section 61 in electrical fitting 60. Each electrical conductor 52 is secured to pin 53 that is sized to slide into a mating sleeve 62 in fitting 60 to complete an electrical interconnection when nut 56 is tightened onto section 61. At least one O-ring 57 on end portion 55 creates a seal between connector 50 and an internal bore 63 in fitting 60.
In many uses an electrically nonconductive and corrosion resistant protective coating 70 measuring about 0.0010±0.005 inches thick is applied to housing 51 of connector 50 by spraying-on coating 70. A protective coating can be applied on fitting 60 as well.
However, protective coating 70 on housing 51 can be formed with irregular surfaces 71 as a consequence of imperfections of the spraying application technique. Irregular surfaces 71 can also be created on housing 51 as a consequence imperfections in the manufacturing process of connector 50.
These irregular surfaces 71 in coating 70 on housing 51 can be troublesome in connectors 50 particularly where housing 51 has an annular-shaped transition end 54 extending outside of an electrical cable 80. Electrical cable 80 can extend from connector 50 through water 5 to connect transducers or other sensors (not shown) to fitting 60 that can act as an electrical hull penetrator outboard of the pressurized hull of a Navy submarine, for example. A waterproof boot 90 is molded about transition end 54 of connector housing 51 and electrical cable 80.
Waterproof boot 90 is the mechanical transition to the outer jacket 81 of electrical cable 80 and is made from a sealing-casting material that cures into boot 90. Boot has a flexible waterproof form that resists sharp bending of cable 80 where it enters and is secured to connector 50 by an internal lock nut (not shown). Casting material is typically a synthetic rubber such as silicone, Neoprene™ or the like having the properties of being waterproof and tough with sufficient flexibility, etc. for reliable operation in the demanding marine environment. Boot 90 bonds to an outer surface 54A and an inner surface 54B of transition end 54. Boot 90 contacts outer surface 54A at an annular interface 92 an annular tapered part 93 provides a transition.
Referring now to FIG. 2, boot 90 is molded by positioning two halves of a mold 95 to define a casting cavity 96 to contain transition end 54 of connector housing 51 and cable 80. Casting chamber 96 of mold 95 is coated with a suitable release agent (not shown) to allow removal of boot 90 after it has cured. Mold 95 has a cable end 95A positionable about outer jacket 81 of electrical cable 80 and a connector end 95B positionable about part of connector 50. Only the bottom half of rigid mold 95 is shown, it being understood that the mirror-image top half of mold 95 is placed over and tightly secured to bottom half to define casting cavity 96 for waterproof boot 90. Mold 95 is then filled with a liquid form of casting material via a open-ended filling cavity 97 at cable end 95A that is in communication with casting cavity 96. Casting material sets or cures into waterproof boot 90. (See FIG. 1.)
Casting cavity 96 is shaped to define waterproof boot 90 and forms a boot termination shoulder 96A for shoulder 93 of boot 90 toward connector end 95B of mold 95. An O-ring groove 95C is adjacent boot termination shoulder 96A to receive an O-ring 95D, and a connector shoulder cavity 95E is by inward flange 95F at connector end 95B of mold 95.
During the casting procedure of waterproof boot 90 in mold 95, filling cavity 97 faces upward and connector 50 has a shoulder 72 against inward flange 95F in connector shoulder cavity 95E and has transition end 54 fitted into O-ring 95D to hold and prevent leakage of liquid casting material. The other half (not shown) of mold 95 is fitted so that O-ring 95D is positioned to annularly coextend in the other half of termination shoulder O-ring groove 95C. Mold 95 is then filled with liquid sealing-casting material.
Casting material of boot 90 bonds or adheres to outer jacket 81 of electrical cable 80 along the length of cable 80 covered by boot 90 in a watertight sealed relationship and this bonding prevents any leaking of ambient water 5 along the juncture between outer jacket 81 and boot 90. However, water 5 can and does leak into connector 50 due to imperfections 71 or unevenness of protective coating 70 on transition end 54 of housing 51.
Leakage of water 5 compromises reliable operation of connector 50 due to irregularities 71 in protective coating 70 on transition end 54 of housing 51. These irregularities 71 are exposed to ambient water 5 at an annular interface 92 on transition end 54 near the center of housing 51 at the end of waterproof boot 90. Leakage of water 5 at annular interface 92 is likely to occur because of imperfections of application of coating 70. Water 5 which has leaked through annular interface 92 seeps under annular tapered part 93 of boot 90 and to the left along annular interface 54 between boot 90 and along the top 54A of transition end 54. Next, leaked water 5 goes back to the right toward fitting 60 between boot 90 and along the bottom 54B of transition end 54 and onward into connector 50 to disrupt reliable operation of its other internal constituents.
Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for a cost-effective improvement for underwater connectors that prevents water leakages attributable to irregularities in protective coatings.